1. Field of the Invention
The invention relates to a developing apparatus and image forming equipment and method thereof. More particularly, the present invention relates to a developing apparatus and image forming equipment and method for preventing a developing agent from contaminating the image forming apparatus.
2. Description of the Related Art
Image forming equipment such as a laser printer, a light emitting diode (LED) printer, a digital copier, a facsimile for general paper, and so on, have a function of transferring an image signal based on an input digital signal to a printing medium, such as a sheet of paper, in a form of a visual image and printing it.
This image forming equipment comprises a developing apparatus, a laser scanning apparatus, a fixing apparatus, and so on.
The developing apparatus includes an image carrier such as a photosensitive drum for developing the visual image, and a developer carrier for transferring a developer such as a toner to the image carrier.
For the image carrier, an electrostatic latent image corresponding to the visual image is formed on a surface of the image carrier by light scanned by the laser scanning apparatus.
In an example of the developer carrier, there is a developing roller used for a non-contact developing mode. The developing roller rotates with a predetermined developing gap separated from the image carrier. The developing roller functions to transfer the developer such as the toner to a region for the electrostatic latent image in the non-contact developing mode. In other words, the developer attached to the developing roller is transferred to the electrostatic latent image region through the developing gap by an electrostatic force caused by a potential difference between the electrostatic latent image and the developing roller. The toner transferred to the electrostatic latent image region is transferred to the printing medium passing between the image carrier and the transferring roller. The printing medium passes through the fixing apparatus. The visual image transferred to the printing medium is fixedly attached to the printing medium by high temperature/pressure at the fixing apparatus.
Meanwhile, as the image carrier and the developing roller rotate each other in a forward direction (i.e. in a direction rotating in engagement with each other), a constant air stream occurs at the developing gap. Further, as the printing medium moves, such an air stream occurs between the printing medium and the developing apparatus.
Particles of the toner, which are transferred from the developing roller to the electrostatic latent image region through the developing gap, are disturbed by the air stream. In particular, the toner particles lacking in charge are impacted more by the influence of the air stream compared with the electrostatic force, and are not transferred to the electrostatic latent image region. Further, some toner particles are scattered to an interior of the image forming equipment, thus contaminating the interior of the image forming equipment.